Sex without condoms

Recently my boyfriend and I tried sex without a condom and it is amazing! So much better than with a condom for both of us. I have the mirena IUD in and he pulled out as well so I thought we were being pretty safe. We had sex with a condom this morning and it just isn’t as good with one and I wanted to advice on how safe is would be to have sex without a condom and me with my mirena. He is 20 and I’m 19 and we are very much in love and plan on getting married in the future but kids right now with us both in university isn’t ideal. What are the chances of us getting pregnant with the mirena and him pulling out? (And I know the pull out is really unreliable)